TH350 vs. TH400: Which Transmission is Right for Your Build?

When it comes to building or upgrading your vehicle, one of the most important decisions you’ll encounter is which transmission to choose. For many enthusiasts, the choice often comes down to two incredible options from General Motors: the TH350 and the TH400. Both transmissions are celebrated for their durability, performance, and versatility, yet they have unique differences that may make one a better fit for your specific needs.

Let’s explore the key characteristics, benefits, and drawbacks of each transmission, empowering you to make a decision that aligns perfectly with your vehicle’s requirements. Whether your project is a classic car, street rod, off-road build, or high-performance racing vehicle, gaining a clear understanding of the TH350 and TH400 will guide you in selecting the best transmission for your exciting project!

What Are the TH350 and TH400?

Before we dive into the comparison, let’s start with a brief overview of the TH350 and TH400 transmissions.

TH350 Transmission:

The Turbo-Hydramatic 350 (TH350) is a three-speed automatic transmission designed and built by General Motors (GM). Introduced in 1969, it quickly became one of the most widely used automatic transmissions for cars, trucks, and SUVs. The TH350 was engineered to be a reliable, compact, and cost-effective solution for medium-duty applications, offering a balance of performance and efficiency.

TH400 Transmission:

The Turbo-Hydramatic 400 (TH400) is a three-speed automatic transmission built by GM, initially introduced in 1964. While it shares some similarities with the TH350, the TH400 is designed for heavier-duty applications. It's larger, stronger, and can handle significantly more power and torque than the TH350, making it the go-to choice for high-performance vehicles, heavy-duty trucks, and applications where high-torque demands are common.

Key Differences Between the TH350 and TH400

While both the TH350 and TH400 are great choices for various builds, there are some key differences that set them apart. Here are the most important factors to consider:

1. Torque Capacity:

• TH350: The TH350 is rated to handle up to 350 lb-ft of torque in its stock form, making it ideal for most street applications, light-duty trucks, and performance builds with moderate horsepower.

• TH400: The TH400, on the other hand, is designed to handle up to 450 lb-ft of torque or more in stock form. This makes it a better choice for high-performance and heavy-duty applications where the engine produces higher torque, such as drag racing or towing heavy loads.

2. Size and Weight:

• TH350: The TH350 is more compact and lighter than the TH400. This makes it a great choice for smaller builds, like muscle cars or street rods, where space and weight savings are important.

• TH400: The TH400 is larger and heavier, designed for larger vehicles and more extreme applications. The added size and weight contribute to its strength and durability but may be an issue if you're working with a space-constrained build.

3. Durability:

• TH350: The TH350 is durable enough for most street-driven cars, trucks, and moderate performance builds. However, it's not as strong as the TH400 in extreme conditions, especially when it comes to handling higher horsepower and torque.

• TH400: The TH400 is built to withstand much more abusive conditions. It’s typically found in heavy-duty vehicles and high-performance applications, making it more suitable for extreme performance builds, including drag racing, towing, and off-road driving.

4. Gear Ratios:

Both the TH350 and TH400 have similar gear ratios, but the primary difference is that the TH400 has a lower first gear, which provides more torque multiplication and is better suited for towing and hauling.

• TH350 Gear Ratios:
  

• 1st: 2.52:1

• 2nd: 1.52:1

• 3rd: 1.00:1

• TH400 Gear Ratios:
  

• 1st: 2.48:1

• 2nd: 1.48:1

• 3rd: 1.00:1

While the differences are minor, the TH400’s slightly lower first gear gives it an edge when it comes to launching heavy vehicles or vehicles with more torque.

5. Performance and Upgrades:

• TH350: The TH350 is a popular choice for mild to moderate performance applications. It's highly customizable with shift kits, torque converters, and other performance parts to suit various needs. It’s great for builds where reliability and efficiency are the primary goals.

• TH400: The TH400 is often preferred for high-performance and racing builds, as it can be modified to handle extreme horsepower and torque. With the right upgrades, the TH400 can be built to handle 1000+ horsepower, making it a favorite for drag racing and other high-stress applications.

Which Transmission is Right for Your Build?

Now that we've gone over the key differences, let's take a closer look at which transmission is best suited for different applications.

1. Daily Drivers and Street Builds:

For daily drivers and mild street builds, the TH350 is likely your best option. It's more compact, lighter, and more fuel-efficient compared to the TH400, which makes it a great fit for muscle cars and classic street rods.

The TH350 can easily handle moderate horsepower (up to around 350-400 hp), and with the right upgrades, it will provide solid performance for everyday driving needs.

2. High-Performance Builds:

If you’re building a high-performance vehicle or planning to push your car to the limit with drag racing or track racing, the TH400 is the superior option. Its ability to handle higher horsepower and torque makes it the go-to choice for high-performance enthusiasts.

The TH400’s durability and strength mean that it can handle the extreme power generated by performance engines. If you're building a drag racing car, a pro-touring build, or a vehicle designed for high torque applications, the TH400 will ensure you get the reliability and performance you need.

3. Heavy-Duty Towing or Off-Road Applications:

For towing or off-road applications, the TH400 is the best choice due to its superior torque handling capacity and ability to withstand the stress of heavy loads. It's commonly used in trucks and SUVs built for off-road use and is ideal for applications like towing and hauling heavy trailers.

The TH350 may not be able to handle the same heavy loads or extreme conditions as the TH400, so for anything that involves substantial weight or power, the TH400 should be your transmission of choice.

4. Budget Builds:

If you're working with a budget build where performance isn’t the primary focus, the TH350 is a great, cost-effective option. It's cheaper than the TH400 and easier to maintain. For projects where budget constraints are important, but you still want a reliable transmission, the TH350 offers a balance of performance and value.

TH350 vs. TH400 – Making the Right Choice

Ultimately, the choice between the TH350 and the TH400 comes down to your specific needs and goals for your build.

• If you're looking for a cost-effective, lightweight transmission for street use or moderate performance, the TH350 is your go-to choice.

• If you need a high-torque, heavy-duty transmission for racing, towing, or extreme performance builds, the TH400 is the superior option.

Both transmissions have earned their place in the world of performance vehicles and enthusiast builds, and either one will provide years of reliable service when chosen appropriately. With the right upgrades, both the TH350 and TH400 can be tailored to meet the needs of a wide range of automotive projects.

At Monster Transmission, we offer both TH350 and TH400, ensuring you have access to the best transmissions for your next build. Whether you’re restoring a classic or building a high-performance vehicle, we can help guide you in the right direction.

If you're ready to upgrade, check out our TH350 and TH400 transmission options and start building the vehicle of your dreams today!